Critical Thinking: Definition, Skills and How to Improve

Critical thinking is careful, reflective reasoning used to decide what to believe or what to do. It involves interpreting information accurately, analysing arguments, judging the quality of evidence, drawing well-supported conclusions and checking your own thinking for errors and bias. Philosopher Robert Ennis's short definition is widely used: critical thinking is "reasonable reflective thinking focused on deciding what to believe or do."

Critical thinking is not the same as being critical in the everyday sense of finding fault. A good critical thinker applies the same standards to ideas they like as to ideas they dislike, and is willing to change their mind. It draws on cognitive psychology, logic and the study of cognitive biases, and it is central to science, medicine, law and everyday decisions.

Where the Idea Comes From

The roots of critical thinking go back to Socrates, whose method of probing questions exposed contradictions in confident beliefs. In modern education, the key figure is John Dewey, whose 1910 book How We Think described "reflective thinking": the active, persistent and careful consideration of a belief in light of the grounds that support it and the conclusions it leads to.

In 1990, philosopher Peter Facione led a panel of 46 experts in a structured consensus exercise for the American Philosophical Association, now known as the Delphi Report. It described critical thinking as purposeful, self-regulatory judgment, and it separated the skills of critical thinking from the dispositions, or habits of mind, that make people use those skills. That distinction remains central: knowing how to evaluate evidence is of little use if you only do it for claims you already dislike.

Psychologists such as Diane Halpern and Keith Stanovich later linked critical thinking to research on reasoning and decision-making, showing that good thinking depends on both ability and the motivation to override quick, intuitive answers.

Core Components: Skills and Dispositions

The Delphi Report's six core skills give a useful map of what critical thinking involves:

Dispositions matter as much as skills. The Delphi panel described the ideal critical thinker as habitually inquisitive, well-informed, open-minded, fair-minded in evaluation, honest in facing personal biases, prudent in making judgments and willing to reconsider. Philosophers Richard Paul and Linda Elder describe similar "intellectual virtues", including intellectual humility (knowing the limits of what you know), intellectual courage (taking unpopular ideas seriously) and intellectual empathy (understanding views you reject well enough to state them fairly).

Types of Reasoning

Deductive reasoning

In deductive reasoning, the conclusion follows necessarily from the premises. The classic example: all humans are mortal; Socrates is human; therefore Socrates is mortal. An argument is valid if the conclusion must be true whenever the premises are true, and sound if it is valid and its premises really are true. A valid argument with a false premise can still lead to a false conclusion. Two common valid forms are modus ponens (if P then Q; P; therefore Q) and modus tollens (if P then Q; not Q; therefore not P).

Inductive reasoning

Inductive reasoning moves from specific observations to general conclusions that are probable rather than certain. Every swan Europeans had seen for centuries was white, so they concluded all swans were white, until black swans were found in Australia. Most everyday and scientific reasoning is inductive: we generalize from samples, reason by analogy and infer causes from patterns. Its strength depends on the size and representativeness of the sample and on ruling out alternative explanations, which is why research methods such as random sampling and control groups matter.

Abductive reasoning

Abductive reasoning, or inference to the best explanation, starts with an observation and asks which explanation best accounts for it. The grass is wet, so it probably rained, unless the sprinklers were on. Doctors, detectives and scientists reason abductively, then test their best explanation. Good explanations are simple, consistent with other knowledge and able to account for all the evidence, and good abductive reasoners keep alternatives in view.

Common Logical Fallacies

A fallacy is a pattern of reasoning that seems persuasive but does not support its conclusion. Formal fallacies are errors in the logical structure itself. Informal fallacies have a valid-looking structure but fail because of their content, relevance or assumptions.

Spotting a fallacy does not prove a conclusion false; it shows only that this particular argument does not establish it. Accusing opponents of fallacies can itself become a way of avoiding their best points, which is why good critical thinkers also practise steel-manning: restating an opposing argument in its strongest form before responding.

Argument Analysis

Philosopher Stephen Toulmin's 1958 model breaks everyday arguments into parts, which helps reveal where they are weak:

• Claim: the conclusion being argued for.
• Grounds (data): the evidence offered.
• Warrant: the often unstated assumption linking the evidence to the claim.
• Backing: support for the warrant.
• Qualifier: how strongly the claim is made ("probably", "in most cases").
• Rebuttal: conditions under which the claim would not hold.

Take the argument "This supplement works, because thousands of customers say they feel better." The warrant, that customer testimonials reliably show a product works, is weak: people who feel no change rarely write reviews, and many people improve on their own or through the placebo effect. Identifying the warrant shows exactly where to push.

When evaluating any argument, ask four questions: Are the premises true (acceptability)? Are they relevant to the conclusion (relevance)? Is there enough evidence (sufficiency)? And have strong counterarguments been addressed?

Cognitive Biases and Critical Thinking

Much of what makes critical thinking hard is not lack of logic but the way human judgment works. Daniel Kahneman's distinction between fast, intuitive "System 1" thinking and slow, deliberate "System 2" thinking captures the problem: intuitive answers arrive quickly and feel right, and checking them takes effort.

Shane Frederick's Cognitive Reflection Test illustrates this. One item reads: a bat and a ball cost $1.10 in total; the bat costs $1.00 more than the ball; how much does the ball cost? The answer that springs to mind is 10 cents, but the correct answer is 5 cents. Many students at top universities get it wrong, not because they cannot do the arithmetic but because they do not stop to check.

Several biases are especially relevant:

• Confirmation bias and its identity-driven form, myside bias, lead people to seek and favor evidence for what they already believe.
• The availability heuristic and base rate neglect distort judgments of risk and probability.
• Anchoring pulls estimates toward an initial number.
• The Dunning-Kruger effect describes how people with limited skill in an area can overestimate their competence.

A key finding from Keith Stanovich and Richard West is that intelligence offers little protection against some of these biases. Stanovich uses the term "dysrationalia" for the gap between intelligence and rational thinking. What does help is a set of thinking dispositions, such as "actively open-minded thinking": deliberately seeking evidence against your current view and taking it seriously.

Information Literacy

A large part of critical thinking today is deciding which sources to trust. Research by Sam Wineburg and Sarah McGrew at Stanford compared historians, students and professional fact-checkers evaluating unfamiliar websites. The fact-checkers were far more accurate and faster because they read laterally: instead of studying the website itself, they quickly opened other tabs to see what independent sources said about who was behind it.

Digital literacy researcher Mike Caulfield's SIFT approach summarizes practical steps:

1. Stop. Before sharing or reacting, pause and ask whether you know the source.
2. Investigate the source. Find out who is behind it and what their expertise and motives are.
3. Find better coverage. Look for trusted reporting or research on the same claim.
4. Trace claims to the original. Follow quotes, statistics and images back to where they first appeared, to check context.

Other useful questions include whether a claim comes from a single study or a body of research, whether a study was peer-reviewed, whether it used a control group, and whether a headline matches what the research actually found. Content generated by AI tools needs the same checks, since such tools can produce fluent but incorrect statements and invented references.

Critical Thinking and Problem Solving

Critical thinking supports problem solving at each stage: defining the real problem rather than its symptoms, generating options, evaluating them against clear criteria and reviewing what happened. Tools such as decision matrices, cost-benefit analysis and premortems (imagining a plan has failed and asking why) give structure to these steps. Two classic obstacles are functional fixedness, seeing objects only in their usual role, and mental set, sticking with an approach that worked before, both studied by Gestalt psychologists such as Karl Duncker and Abraham Luchins. Critical thinking also works alongside creativity: creative thinking generates possibilities, and critical thinking judges which are worth pursuing.

Metacognition and Self-Reflection

Metacognition, thinking about your own thinking, is what the Delphi Report called self-regulation. It includes planning how to approach a problem, monitoring whether your reasoning is on track and evaluating afterwards what worked. Practical habits include writing down your reasoning and predictions before outcomes are known, asking "what would change my mind?" about strongly held beliefs, explaining your view to someone who disagrees, and reviewing decisions afterwards to separate good process from good luck.

How to Develop Critical Thinking

Research offers grounds for cautious optimism. In a 2015 meta-analysis of 341 effect sizes, Philip Abrami and colleagues found that instruction aimed at critical thinking produced a moderate average improvement. The most effective approaches combined explicit teaching of critical thinking principles with three ingredients: dialogue (discussion and debate), authentic problems and examples, and mentoring or coaching.

There is an important limit. Cognitive scientist Daniel Willingham argues that critical thinking is not a general skill like riding a bike that transfers easily to any topic. It depends on knowing about the subject: you cannot evaluate a medical study's design without knowing what makes medical studies trustworthy. This is why people who reason well in their own field can reason poorly outside it. Practical implications:

• Learn content and thinking together. Practise evaluating evidence within subjects you are studying, not only with abstract puzzles.
• Make principles explicit. Name the concepts, such as correlation versus causation, sample size or base rates, so you can recognize them in new settings.
• Argue the other side. Debating or writing the best case for a view you reject builds both skill and disposition.
• Seek feedback. Teachers, colleagues and peer reviewers catch errors we cannot see in our own work.
• Practise with real information. Analyse news reports, adverts and research summaries, checking claims against original sources.

Our guides to psychology research methods and cognitive biases are good places to build the background knowledge critical thinking depends on.

Measuring Critical Thinking

Several standardized tests aim to measure critical thinking. The Watson-Glaser Critical Thinking Appraisal, first developed in the 1920s and 1930s, is widely used in recruitment and assesses inference, recognition of assumptions, deduction, interpretation and evaluation of arguments. The California Critical Thinking Skills Test, based on the Delphi Report, is used in higher education. The Cornell Critical Thinking Tests and the Ennis-Weir Critical Thinking Essay Test were developed by Robert Ennis and colleagues. The Halpern Critical Thinking Assessment uses everyday scenarios and includes open-ended responses.

These tools have limits. Multiple-choice formats capture recognition of good reasoning more easily than the disposition to use it in real life, and scores depend partly on reading ability and general knowledge. Many educators therefore also use essays, performance tasks and rubrics.

Barriers to Critical Thinking

• Cognitive: limited time and attention, reliance on mental shortcuts and lack of relevant knowledge.
• Emotional: fear of being wrong, attachment to an idea and stress, which narrows attention.
• Social: pressure to agree with a group, which can lead to groupthink; deference to authority; and identity, when beliefs signal which group we belong to.
• Environmental: information overload, distraction and algorithmically curated feeds that show us more of what we already agree with.

Recognizing these barriers is part of critical thinking itself. Many are best managed by changing the situation, for example by slowing down important decisions, inviting dissent or deciding in advance what evidence would change your view.

Conclusion

Critical thinking is less a single skill than a combination of abilities and habits: understanding claims accurately, analysing arguments, weighing evidence, drawing careful conclusions and keeping watch over your own biases. It is demanding because the mind's default is to accept the first plausible answer, especially one that suits us. The research suggests it can be improved through explicit teaching, practice with real content, discussion with people who disagree and steady attention to the quality of evidence. Those habits are useful far beyond the classroom, from evaluating health claims to deciding how to vote.